In a disk array apparatus such as a Redundant Arrays of Inexpensive Disks (RAID) apparatus, it is important to improve the quality of storage units (e.g. a Hard Disk Drive (HDD), to detect failure in the early stage, and to solve problems when storing data requiring high reliability.
In relation to the above importance, in some cases, the control firmware of the HDDs needs to be updated to cope with problems at the worksite.
The completion of updating the firmware of the HDDs in a conventional disk array apparatus requires rebooting of the HDD.
For this reason, conventional disk array apparatuses update the control firmware when the disk array apparatus is powered off for maintenance or others.
There has been provided a technique, for an information processor such as a personal computer, of copying a basic input/output system program in accordance with an updating flag when the operating system is started, and a technique of updating the firmware of a printer when a print operation is completed or when a request to switch the power is issued (see Patent References 1 and 2 below).    [Patent Reference 1] Japanese Patent Application Laid-Open (KOKAI) No. HEI 8-16408    [Patent Reference 2] Japanese Patent Application Laid-Open (KOKAI) No. 2007-69368
As described above, a conventional disk array apparatus is incapable of updating control firmware of HDDs while the apparatus is in normal operation (working).
Therefore, even if the control firmware needs to be updated, the disk array apparatus has to wait for maintenance. Namely, the control firm has not been able to be occasionally updated.
Since a normal disk array apparatus includes from hundreds to thousands of HDDs, it takes a considerable time and workload for the operator to register the control firmware for updating into each individual HDD (i.e., to reboot each individual HDD).